In the field of electric arc welding, it is common practice to use electromagnetic devices such as chokes and transformers in power supplies. For example, as described in Clark et al., U.S. Pat. No. 5,819,934, incorporated by reference herein, a power source, such as a single phase line voltage, may be directed through a transformer to a rectifier in a DC electric arc welder. The output circuit normally includes a capacitor in parallel across the electrode and the workpiece, with a relatively small inductance for charging the capacitor as a rectifier or power supply provides DC current. This inductance removes the ripple from the welding current. And, in series with the arc gap of the welder, there is generally provided a choke capable of handling high currents and used to control current flow for stabilizing the arc.
A transformer (or choke) generally consists of one or more coils (windings) of conducting wire, wound on a former (bobbin) that surrounds the center limb (or sometimes all limbs) of a circuit of magnetic material (core). The winding wires are insulated, and the core is made from thin sheet steel plates known as laminations (this reduces “eddy current” losses). The assembly is typically held together by clamps, which are held in place by long screws that are insulated from the rest of the structure (again, to limit eddy currents). The winding wires are either made off to terminals mounted on the clamps or the wire may leave the coil by leads.
In particular, chokes and transformers commonly have cores made up of individual laminations which may take the form of a butted stack or an interleaved stack. A variety of ways have been used to hold the laminations together to make a core for the device. They have been bolted together. They have been welded together. They have been adhered together. They have been enclosed within a retaining frame. But all these methods are costly because they involve additional components and/or add to the time and number of operations needed to assemble the core. It is desirable, therefore, to improve the ease of assembly by simply press fitting or “snapping together” the main components, while maintaining or improving upon the structural integrity and performance of the choke and transformer cores.